Ethylene or ethene is the simplest alkene with the formula C2H4. Ethylene is produced by methods including pyrolysis, cracking, partial oxidation of hydrocarbons, steam cracking of ethane, or catalytic cracking of heavy olefins. Ethylene is a widely used as a raw material for producing polyethylene, ethylene glycol, ethylene oxide, ethylene dichloride, vinyl chloride and polyethylene. Alternate uses include, welding gases when combusted, anesthetic agents in an 85% ethylene and 15% oxygen mixture, and fruit ripening agents in commercial ripening processes.
Acetylene or ethyne is the simplest alkyne with the formula C2H2. Similar to ethylene, acetylene is produced by pyrolysis, partial oxidation of hydrocarbons, cracking heavier hydrocarbons, and hydrolysis of calcium carbide. Acetylene is used in welding when combusted, incorporated into polymers and plastics, converted to acrylic acids and used in chemical synthesis of other materials. Further, acetylene may be converted to ethylene by hydrogenation.
Propylene or propene is an unsaturated organic compound with the chemical formula, C3H6. Propylene is produced from pyrolysis, as a byproduct of hydrocarbon refining, and the cracking of heavier hydrocarbons. Propylene is a raw material for polymers and plastics, and is converted by various pathways to acetone and phenol. In certain instances, propylene is unstable or highly reactive; particularly, it undergoes addition reactions easily as a gas.
Ethylene, acetylene, and propylene are commercially important light hydrocarbon gases with chemical synthesis applications. Additionally, they are used in liquid hydrocarbon fuel synthesis or as a fuel themselves. However, at standard temperature and pressure (STP) these light hydrocarbons exist as flammable, reactive, colorless gases and therefore are difficult to transport in significant quantities over long distances.